The present invention relates to a wheel rotating speed detector and a method for the installation thereof, also relates to a travelled distance detector and a method for the installation thereof.
A wheel rotating speed detector is used to detect the wheel rotating speed of a motor vehicle, whilst a travelled distance detector is used to detect a travelled distance of a motor vehicle in accordance with the detected wheel rotating speed.
In particular, the present invention relates to a wheel rotating speed detector and a travelled distance detector, all using a navigation system which can indicate a present position of a motor vehicle and tell an azimuth to which the motor vehicle will proceed.
Recently, a navigation system has come into general use for common people when driving a motor vehicle. A conventional navigation system is known to include a GPS (Global Positioning System) and a detecting system. The GPS is used to receive an radio wave from a satellite to detect a present position of a motor vehicle, so as to give instruction about which azimuth the automobile should proceed. The detecting system is also used to detect a present position of a motor vehicle in accordance with output signals from a gyro or a sensor provided in the vehicle.
FIG. 12 illustrates one example of the above-mentioned navigation system. As shown in FIG. 12, a conventional navigation system includes an earth magnetism sensor 1, a gyro 2, a travelled distance sensor 3, a GPS positioning means 4, a controller 5, an input means 14, a display means 15. The earth magnetism sensor 1 is used to detect an azimuth of a motor vehicle in accordance with a detected magnetic field. The gyro 2 is used to detect an angular velocity of a direction change of a motor vehicle. The travelled distance sensor 3 is used to detect a motor vehicle in its stopped condition or a moving condition, and to detect its travelling speed and a travelled distance. The GPS positioning means 4 is used to receive a radio wave from a GPS satellite so as to detect the latitude, longitude, height, proceeding azimuth of a motor vehicle.
The controller 5 is used to control the above magnetism sensor 1, the gyro 2, the travelled distance sensor 3, the GPS positioning means 4, and to perform various calculations using various detected signals from the above elements 1-4, thereby producing various data for use in the navigation system. The input means 14 is used to supply various instructions to the controller 5. The display means 15 is for example a liquid crystal capable of indicating various output signals.
The controller 5 includes an interface 6, CPU (Central Processing Unit) 7, a ROM (Read Only Memory) 8, a RAM (Random Access Memory) 9 and a CD-ROM (Compact Disc-Read Only Memory) 10, a buffer memory 11, a graphic controller 12 and a display controller 13.
The interface 6 is used to feed the output data from the above sensors 1, 3, the gyro 2 and the GPS positioning system 4 into the controller 5 so as to perform A/D conversion. The CPU 7 is used to perform various calculations in accordance with a predetermined program stored in the ROM 8. The RAM 9 is used to write thereinto or read therefrom various data necessary to carry out various calculations. The CD-ROM 10 is used to store therein some information such as a map which can be read out at any time.
The buffer memory 11 comprises a V-RAM which is used to temporarily store a picture data. The graphic controller 12 is used to perform a necessary control when picture data stored in the buffer memory 11 are to be produced. Further, the display controller 13 is used to supply an output from the graphic controller 12 to the display means 15 so as to control its picture display.
The operation of the navigation system of FIG. 12 may be described in detail below.
Upon starting the navigation system, the controller 5 operates to read out from the CD-ROM 10 a data such as a map and a data relating to a present position of a motor vehicle, and store these data into the RAM 9. Then, the controller 5 operates to obtain from the GPS positioning means 4 a latitude data and a longitude data (both of which are used to indicate the present position of a motor vehicle), further a date indicating an azimuth to which a motor vehicle is proceeding. These data are then supplied to the graphic controller 12 so as to be displayed on the display means 15. Further, the present position of a motor vehicle is marked on a map on display, in accordance with the present position and the proceeding direction of the vehicle. Afterwards, information is periodically read from the GPS positioning means 4 so that a present position of a motor vehicle may be periodically indicated on the map on display. If necessary, the map on display may be renewed.
Further, a present position of a motor vehicle may also be detected in accordance with the output signals from the magnetism sensor 1, the gyro 2 and the travelled distance sensor 3. Then, a present position of the motor vehicle detected by the GPS positioning system 4 is compared with a present position detected with the use of the sensors 1, 3 and the gyro 2, so as to produce a signal indicating a difference between the two detected results, which is considered to be a detection error and is then corrected.
In recent years, a newly manufactured motor vehicle is usually provided with an above-described navigation system. However, with an old vehicle manufactured long ago or a cheap vehicle made in order to reduce its price, there is not provided any navigation system. In order to install a navigation system in a motor vehicle, it is necessary for a user to buy a set of elements forming the navigation system and install them himself or ask a skilled technician to perform such installation for him.
Then installing a navigation system in a motor vehicle, as discussed above, it is necessary to include a travelled distance sensor 3. On the other hand, when buying a set of elements forming the navigation system, a user is allowed to remove a travelled distance sensor from his purchasing list since a same sensor originally provided in his vehicle can be used in the navigation system. But, there is task before him. Namely, it is necessary for him to properly connect the original distance sensor to the controller 5 of the navigation system. In detail, an external terminal of a microcomputer containing the original distance sensor should be connected to an interface 6 of the navigation system, so that a signal concerning a travelled distance may be fed from the microcomputer to the navigation system.
However, when a user installs a navigation system into a motor vehicle by himself, it is usually difficult for him to know which external terminal (there are several external terminals) on the microcomputer produces signals concerning wheel rotating speed and vehicle travelled distance. In other words, if a user does not have knowledge about the external terminals of the microcomputer containing the travelled distance sensor, it mill be impossible for him to complete the installation. Moreover, since required knowledge about the external terminals of the microcomputer are not printed on a manual of a motor vehicle, as a result, it is unavoidable for a skilled technician to perform such an installation of a navigation system, this however proves to be an additional expense for a user.